Lost in the dark: where’d all that pesky matter go???
The challenge: To find something in the dark, that you cannot see, whose composition is not fully understood, but yet is present in the universe and as ubiquitous as the light we can see. Such is the quest for so-called ‘dark matter’, and one that our speaker, Dr. Matthew Bothwell (Institute of Astronomy, Cambridge) has been investigating using data from a wide variety of observational sources.
But what is it? This is the question Matt said he almost always got at the end of his talk, and so he started off by positing this right up-front. The conundrum is simple. Using standard techniques, based on observations right across our electromagnetism spectrum from radio all the way through to X-ray and Gamma-ray astronomy, there is simply not enough matter to explain the nature of our universe. Images from the Webb and Hubble telescopes often show the effects of gravitational lensing – when our view of distant galaxies is distorted by foreground objects. But often this effect is also seen in open space, without any massive object in the foreground. So whatever matter is there, it is having an effect on gravity, but not visible to astronomers. Hence, ‘dark’ matter.
This is complex and rather philosophical topic, and also an important and live issue in modern cosmology. And yet Matt deftly and patiently guided the audience through in a very enjoyable 45 minute talk, complete with an explanation of two competing ideas: the WIMP (Weakly Interacting Massive Particle) or the MoND (Modified Newtonian Dynamics) theory. And the lively debate each provokes (including in our own society!). This was reflected in the large number of questions for Matt from the audience: only ended by frantic gestures from our host and Flamsteed chair Bobby, as our time was soon up.
But, happily, I can report that there was some light at the end of this particular tunnel, in the form of not just one but two giant white cakes (this “matter” would, and didn’t, get missed by anyone!). As 2024 marks our 25th anniversary, we briefly took the opportunity to celebrate this milestone in the history of the Flamsteed Astronomy Society. There are more events to come: watch this space…!
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